In the manufacture of eyeglasses a proper understanding of the spatial, angular and dimensional relationships between the lens, the frame, and the wearers head and facial portions which support the frame is necessary if the eyeglasses are to function at an optimum level. For example, where the lens is bi- or trifocal, the line or lines of demarcation between the lens sections should be positioned in the frame such that the wearer can comfortably, selectively and effectively view thru the sections without interference from the boundary lines therebetween. Further, for example, where the frame is not well fitted, within fairly close tolerances, to the bridge of the nose, the aforesaid boundary lines will interfere with vision as the frame slips or moves on the wearers nose. The ability then of the technician or optician to take the measurements which are needed for a proper understanding of the aforesaid relationships can make the difference between a good pair of eyeglasses and a non-useable pair.
The conventional methods for taking measurements for eyeglass fittings have remained virtually unchanged since the time they were deemed necessary in the alignment and fitting of the lens in the frame and of the frame to the head. Typically a hand or pocket millimeter ruler is used to take the measurements for the manufacturing and fitting processes. A visual inspection is then used with nothing more than trial and error for the fitting and adjusting of the finished product. The relatively loose tolerances for these measurements have long been set by the American National Standards Institute (ANSI) and haven't changed significantly over the years. The net results of these methods and standards are that fittings of the lens and frames are less than of maximum effectiveness, and offtimes of even non-useable quality.